Stranger, Fan, or Peer? A Systematic Study on the Role of Interlocutor in Persona-Based Dialogue Generation
Organizations: Fondazione Bruno Kessler, Via Sommarive 18, Povo, Trento, Italy · University of Groningen, Netherlands
Abstract
Persona-based dialogue systems are usually conditioned on speaker biography, but dialogues involve at least two participants, and who has access to whose biography can vary across training, inference, and evaluation. Prior work often neglected these aspects, obscuring mechanisms that only appear when biography visibility is toggled separately across training, inference, and evaluation, a three-stage factorisation that prior work has largely treated as a single factor. We study this factorisation on a dataset of dialogues paired with speaker's biographies, varying whether the target and interlocutor speakers see each other's biographies during training and inference, and using an LLM as a judge to perform author identification. We find that (i) training-time visibility, more than inference-time visibility, determines whether models express persona traits through dialogue or fall back on copying biographical text (a known problem/phenomenon in persona-based generation); (ii) models trained with interlocutor-biography visibility copy less target-biographical text than models trained without it, while changing visibility only at inference time has a less consistent effect; and (iii) under asymmetric disclosure, where only the interlocutor sees the target biography, target content leaks into interlocutor turns more often, and dialogues containing such traces are easier for the judge to identify, especially when interlocutor turns are visible. These results suggest that biography leakage into generated turns is an artefact of how interlocutor visibility is configured across training and inference, and separating the three stages is necessary.
Figures & tables
| (a) Judge accuracy by evaluation condition | |
|---|---|
| Both | 0.914 |
| Bio | 0.885 |
| Turns | 0.667 |
| Both | 0.621 |
| (b) Rare-word overlap (%) by direction | |
| Bio Turn | 5.84 |
| M z-s | Trn | Trn | ||||
| Inf | Inf | Inf | Inf | Inf | Inf | |
| Accuracy | ||||||
| Both | 0.936 | 0.953 | 0.830 | 0.854 | 0.803 | 0.831 |
| Bio | 0.963 | 0.957 | 0.848 | 0.834 | 0.814 | 0.793 |
| Turns | 0.939 | 0.947 | 0.789 | 0.818 | 0.746 | 0.782 |
| Both | 0.971 | 0.962 | 0.760 | 0.765 | 0.683 | 0.672 |
| Trn | Trn | |||
|---|---|---|---|---|
| Fam. | Unfam. | Fam. | Unfam. | |
| Acc (avg. evals) | 0.87 | 0.76 | 0.84 | 0.71 |
| Bio Turn | 3.20 | 4.28 | 2.45 | 3.32 |
| Metric | Trn | Trn | Gold |
|---|---|---|---|
| distinct-1 | 0.801 | 0.833 | 0.878 |
| distinct-2 | 0.986 | 0.989 | 0.954 |
| self-BLEU | 3.89 | 4.16 | 7.15 |
| turn coherence | 0.207 | 0.194 | 0.238 |
| persona contradiction | 0.279 | 0.278 | 0.314 |
| M z-s | Trn | |||
| Inf | Inf | Inf | Inf | |
| Accuracy | ||||
| Both | 0.936 | 0.952 | 0.830 | 0.873 |
| Bio | 0.963 | 0.965 | 0.848 | 0.847 |
| Turns | 0.939 | 0.954 | 0.789 | 0.843 |
| Both | 0.971 | 0.971 | 0.760 | 0.779 |
| Comparison | Effect | 95% CI | |
| Fan effect on accuracy | |||
| Both | pp | [3.04, 5.53] | |
| Turns | pp | [4.02, 6.86] | |
| Bio | pp | [ 1.35, 1.03] | 0.820 |
| Fan effect on leakage | |||
| Bio Turn | pp | [0.27, 1.58] | 0.007 |
| Familiar | Unfamiliar | |||
|---|---|---|---|---|
| Inf | Inf | Inf | Inf | |
| Acc. (avg. eval.) | 0.865 | 0.877 | 0.763 | 0.805 |
| Bio Turn | 2.560 | 3.200 | 1.880 | 3.000 |
Appendix figures & tables23 assets
Supplementary material from the paper’s appendix.
Appendix
| Setting | Value |
|---|---|
| Fine-tuning | |
| LoRA | rank 16, alpha 32, dropout 0 |
| Optimizer | AdamW, lr 2e-5, weight decay 0.01 |
| Schedule | cosine, warmup 0.03 |
| Batch | size 4 grad-accum 8, 3 GPUs |
| Training | up to 10 epochs (early stopping) |
| M | Trn | ML | |
| Accuracy | |||
| Both Disc | 0.953 | 0.840 | 0.831 |
| Bio Disc | 0.957 | 0.819 | 0.793 |
| Turns Disc | 0.947 | 0.782 | 0.782 |
| Both Mask | 0.962 | 0.712 | 0.672 |
| % Rare Words | |||
| M | Trn | ML | |
| Familiar (Acc.) | 0.990 | 0.852 | 0.848 |
| Unfamiliar (Acc.) | 0.928 | 0.741 | 0.711 |
| % Rare Words — Familiar | |||
| Bio Trg Turn Trg | 42.080 | 2.773 | 2.827 |
| Bio Int Turn Trg | 38.347 | 2.613 | 2.400 |
| Bio Trg Turn Int | 28.587 | 3.307 | 2.453 |
| Eval. condition | Interlocutor bio | Interlocutor turns |
|---|---|---|
| Both | visible | visible |
| Bio | visible | masked |
| Turns | masked | visible |
| Both | masked | masked |
| pp | 95% CI | ||
| Trn Trn , at Inf | |||
| leakage | [ 0.78, 0.59] | 0.845 | |
| accuracy | [ 0.39, 1.92] | 0.214 | |
| Leakage, Inf Inf | |||
| under Trn | [0.27, 1.58] | 0.007 | |
| under Trn | [ 0.32, 1.07] | 0.327 | |
| Accuracy | % Rare-word overlap | |||||||
|---|---|---|---|---|---|---|---|---|
| Training | Inference | Both | Bio | Turns | Both | Bio Turn | Bio Turn | Bio Turn |
| Trn | Inf | 0.833 | 0.848 | 0.790 | 0.759 | 4.34 | 1.78 | 2.63 |
| Inf | 0.881 | 0.863 | 0.839 | 0.783 | 3.86 | 1.60 | 2.99 | |
| Inf | 0.850 | 0.833 | 0.822 | 0.748 | 4.09 | 2.06 | 2.86 | |
| Trn I+I- | Inf | 0.808 | 0.811 | 0.730 | 0.690 | 3.13 | 1.19 | 2.31 |
| Inf | 0.860 | 0.826 | 0.804 | 0.713 | 3.18 | 1.10 | 2.47 | |
| Eval | Bio Trg Turn Trg | Bio Int Turn Trg | Bio Trg Turn Int | Acc |
|---|---|---|---|---|
| Both Disc | 0.033 | 0.033 | 0.032 | 0.914 |
| Bio Disc | 0.033 | 0.033 | 0.032 | 0.885 |
| Turns Disc | 0.033 | 0.033 | 0.032 | 0.667 |
| Both Mask | 0.033 | 0.033 | 0.032 | 0.621 |
| Inf. | Eval | Bio Trg Turn Trg | Bio Int Turn Trg | Bio Trg Turn Int | Acc |
|---|---|---|---|---|---|
| Inf | Both Disc | 0.038 | 0.042 | 0.046 | 0.830 |
| Bio Disc | 0.038 | 0.042 | 0.046 | 0.848 | |
| Turns Disc | 0.038 | 0.042 | 0.046 | 0.789 | |
| Both Mask | 0.038 | 0.042 | 0.046 | 0.760 | |
| Inf | Both Disc | 0.038 | 0.042 | 0.040 | 0.873 |
| Bio Disc | 0.038 | 0.042 | 0.040 | 0.847 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.865 | 0.877 | 0.864 | 0.879 |
| Unfamiliar | 0.763 | 0.804 | 0.731 | 0.772 |
| METEOR — Familiar | ||||
| Bio Trg Turn Trg | 0.038 | 0.037 | 0.038 | 0.038 |
| Bio Int Turn Trg | 0.044 | 0.044 | 0.037 | 0.037 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.829 | 0.857 | 0.804 | 0.844 |
| Unfamiliar | 0.790 | 0.820 | 0.778 | 0.798 |
| Inf. | Eval | Bio Trg Turn Trg | Bio Int Turn Trg | Bio Trg Turn Int | Acc |
|---|---|---|---|---|---|
| Inf | Both Disc | 0.028 | 0.032 | 0.035 | 0.803 |
| Bio Disc | 0.028 | 0.032 | 0.035 | 0.814 | |
| Turns Disc | 0.028 | 0.032 | 0.035 | 0.746 | |
| Both Mask | 0.028 | 0.032 | 0.035 | 0.683 | |
| Inf | Both Disc | 0.028 | 0.032 | 0.028 | 0.849 |
| Bio Disc | 0.028 | 0.032 | 0.028 | 0.823 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.834 | 0.845 | 0.830 | 0.847 |
| Unfamiliar | 0.707 | 0.755 | 0.669 | 0.711 |
| METEOR — Familiar | ||||
| Bio Trg Turn Trg | 0.028 | 0.028 | 0.028 | 0.028 |
| Bio Int Turn Trg | 0.034 | 0.034 | 0.028 | 0.027 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.783 | 0.819 | 0.758 | 0.794 |
| Unfamiliar | 0.745 | 0.775 | 0.723 | 0.752 |
| Inf. | Eval | Bio Trg Turn Trg | Bio Int Turn Trg | Bio Trg Turn Int | Acc |
|---|---|---|---|---|---|
| Inf | Both Disc | 0.037 | 0.042 | 0.045 | 0.832 |
| Bio Disc | 0.037 | 0.042 | 0.045 | 0.844 | |
| Turns Disc | 0.037 | 0.042 | 0.045 | 0.786 | |
| Both Mask | 0.037 | 0.042 | 0.045 | 0.753 | |
| Inf | Both Disc | 0.037 | 0.041 | 0.038 | 0.873 |
| Bio Disc | 0.037 | 0.041 | 0.038 | 0.846 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.864 | 0.879 | 0.864 | 0.875 |
| Unfamiliar | 0.759 | 0.794 | 0.732 | 0.777 |
| METEOR — Familiar | ||||
| Bio Trg Turn Trg | 0.038 | 0.037 | 0.037 | 0.036 |
| Bio Int Turn Trg | 0.044 | 0.043 | 0.036 | 0.036 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.820 | 0.847 | 0.804 | 0.842 |
| Unfamiliar | 0.792 | 0.819 | 0.777 | 0.802 |
| Inf. | Eval | Bio Trg Turn Trg | Bio Int Turn Trg | Bio Trg Turn Int | Acc |
|---|---|---|---|---|---|
| Inf | Both Disc | 0.032 | 0.036 | 0.038 | 0.824 |
| Bio Disc | 0.032 | 0.036 | 0.038 | 0.825 | |
| Turns Disc | 0.032 | 0.036 | 0.038 | 0.757 | |
| Both Mask | 0.032 | 0.036 | 0.038 | 0.707 | |
| Inf | Both Disc | 0.032 | 0.036 | 0.031 | 0.862 |
| Bio Disc | 0.032 | 0.036 | 0.031 | 0.830 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.839 | 0.856 | 0.845 | 0.852 |
| Unfamiliar | 0.732 | 0.771 | 0.705 | 0.740 |
| METEOR — Familiar | ||||
| Bio Trg Turn Trg | 0.032 | 0.032 | 0.031 | 0.031 |
| Bio Int Turn Trg | 0.038 | 0.038 | 0.031 | 0.031 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.806 | 0.839 | 0.789 | 0.815 |
| Unfamiliar | 0.758 | 0.784 | 0.748 | 0.768 |
| Inf. | Eval | Bio Trg Turn Trg | Bio Int Turn Trg | Bio Trg Turn Int | Acc |
|---|---|---|---|---|---|
| Inf | Both Disc | 0.092 | 0.090 | 0.102 | 0.936 |
| Bio Disc | 0.092 | 0.090 | 0.102 | 0.963 | |
| Turns Disc | 0.092 | 0.090 | 0.102 | 0.939 | |
| Both Mask | 0.092 | 0.090 | 0.102 | 0.971 | |
| Inf | Both Disc | 0.093 | 0.091 | 0.095 | 0.952 |
| Bio Disc | 0.093 | 0.091 | 0.095 | 0.965 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.993 | 0.996 | 0.996 | 0.996 |
| Unfamiliar | 0.894 | 0.919 | 0.880 | 0.921 |
| METEOR — Familiar | ||||
| Bio Trg Turn Trg | 0.092 | 0.092 | 0.085 | 0.084 |
| Bio Int Turn Trg | 0.093 | 0.094 | 0.083 | 0.083 |
| Inf | Inf | Inf I+I- | Inf | |
| Accuracy (mean over eval. conditions) | ||||
| Familiar | 0.955 | 0.964 | 0.938 | 0.953 |
| Unfamiliar | 0.950 | 0.958 | 0.944 | 0.956 |
| Eval | No ov. | Ov. | pp |
| M z-s / Inf | |||
| Both | 0.919 (3123) | 0.980 (1252) | |
| Turns | 0.921 (3123) | 0.984 (1252) | |
| M z-s / Inf | |||
| Both | 0.935 (2992) | 0.988 (1383) | |
| Turns | 0.937 (2992) | 0.991 (1383) | |
Persona-Conditioned Generation
Persona-conditioned generation uses profiles, traits, or histories to steer AI outputs toward specified identities, preferences, and behaviors.
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